As an example of a rectifying device of a conventional vehicle AC generator, a horseshoe-shaped heat sink for cooling a rectifying element is disclosed in Patent Document 1. In the heat sink, a plurality of fins, each of which extend radially, is disposed. In the heat sink, damage to the fins caused by fins entangling with each other is prevented by forming a part of the fins to be thick in the outer peripheral end side.
Patent Document 2 discloses a type of press-fitting and the fixing of a rectifying element in a cooling heat sink, where a plurality of fins of the heat sink extends in a direction perpendicular to the press-fitting direction of the element, and these fins extend in parallel with each other (see FIG. 7 in Patent Document 2).
Patent Document 1: Japanese Patent No. 3527516
Patent Document 2: WO 2011/070280
Of conventional heat sinks, the configuration disclosed in Patent Document 1 is reviewed first. In a configuration of a heat sink of which the pitch is relatively narrow and the length in the radial direction and the length in the axis direction are both long, in order to improve the cooling efficiency, a mold may be opened in the radiation direction in the fin molding area, since a taper, which is always generated in a molded product, cannot be ignored (first pattern). In this case, a storage efficiency in the space in the substantially cylindrical generator improves, but this configuration makes the mold complicated and takes more manufacturing space than other types, which means that productivity is not improved.
The mold may be opened in the axis direction (second pattern). In this case, the mold moving space efficiency is improved but a flow passage for axial flow generated by the rotor fan becomes narrow (narrows down in the direction toward a base, which is an element support unit), that is, the cooling efficiency may deteriorate.
If a thick portion is created on the outer peripheral end side of the fins to prevent entanglement, as described in FIG. 10 of Patent Document 1, normally the mold must be opened in the axis direction, hence it is unavoidable that the tapers in the fins deteriorate the cooling efficiency. Thus the configuration disclosed in Patent Document 1 has merits and demerits in terms of the selection of manufacturing processes.
The configuration in Patent Document 2, on the other hand, discloses that the heat sink base main unit is a flat plate, and a plurality of fins extends in parallel with one another, but the fins can still become entangled with each other, even if the entanglement is less frequent than the fins which are disposed radially and of which intervals expand toward the outer periphery, as disclosed in Patent Document 1. If the thickness of the end portions of the fins is partially increased in the configuration of Patent Document 2, however, the mold must be opened during manufacturing in the axis direction, and as a result, the cooling flow for radiation in the axis direction becomes narrow, or the fin pitch must be decreased to prevent this narrowing, which means that productivity cannot be improved.